As is well known, the most crucial data in a pattern-based machine-translation apparatus are verbal-phrase patterns.
The roles played by the verbal-phrase patterns in a machine-translation apparatus are two-fold: firstly, to convert precisely a lexicon such as verbs, adverbial prepositions and objective prepositions used in input simple sentences into a corresponding target language as a means to resolve lexical polysemy; and, secondly, to rearrange accurately order of words when a structure of every component of a source language is converted to a completely different target language from a viewpoint of linguistic structure.
Because performance of a verbal-phrase pattern matching has a great influence upon an over-all system in a pattern-based translation apparatus, it is necessary to construct a large amount of high-quality verbal-phrase patterns in order to improve performance of the apparatus.
If pre-constructed semantics-based verbal-phrase patterns are used, each case component is converted to semantic information so that accuracy of pattern matching is enhanced and conversion of a corresponding verb into a target word becomes accurate.
In this case, while the matching accuracy is enhanced, rate of reproduction becomes too low, because semantic codes of all case components of the patterns are referenced when the matching is carried out. Analysis of illustrative cases of pattern application shows that subjective semantic information has little influence on conversion of verbs and word orders. Hence, it would be inefficient to attach the semantic code and supervise them in the course of constructing a large amount of patterns.
Since the pattern is determined based on the semantics in the pre-constructed semantic-based verbal-phrase patterns, it is necessary to construct all the patterns by semantic codes equivalent to an objective case of the pattern.
For example, about 70% of the verbs of Korean language are Chinese verbs and most Chinese verbs have fixed target words and word orders regardless of semantic information of objective components. As such, if Korean-Chinese verbal-phrase patterns are constructed as pre-constructed verbal-phrase patterns and a verbal-phrase pattern is generated for each case-component structure, then for enough number of verbs there will be hundreds of redundant patterns. This implies that, unless verbal-phrase patterns are constructed with a variety of semantics of Korean verbs taken into account, a number of verbal-phrase patterns to construct increases dramatically, posing a primary obstacle to enhancement of the performance of a translation apparatus.